Stoichiometry Unit 6

1
StoichiometryUnit 6

• Mrs. Mansberger

2
Chemical Stoichiometry
Stoichiometry - The study of quantities of
materials consumed and produced in chemical
reactions.
3
Best Ever Chewy Chocolate Chunk Cookies

• DIRECTIONS
• Preheat the oven to 375 degrees F (190 degrees
  C).
• In a medium bowl, cream together the butter,
  chocolate syrup, brown sugar and white sugar
  until smooth. Beat in the eggs, one at a time,
  then stir in the corn syrup and vanilla. Combine
  the flour, baking soda and salt stir into the
  creamed mixture until just blended. Mix in the
  chocolate chunks by hand. Drop cookies by 1/4
  cupfuls onto ungreased cookie sheets.
• Bake for 12 to 14 minutes in the preheated oven.
  Allow cookies to cool on baking sheet for 5
  minutes before removing to a wire rack to cool
  completely.

• INGREDIENTS
• 1/2 cup butter, softened
• 1/3 cup chocolate syrup
• 1 cup packed brown sugar
• 1/2 cup white sugar
• 2 eggs
• 2 tablespoons corn syrup
• 2 teaspoons vanilla extract
• 2 1/2 cups all-purpose flour
• 1 teaspoon baking soda
• 1/2 teaspoon salt
• 1 (11.5 ounce) package semi-sweet chocolate
  chunks
• Recipe makes 3 dozen cookies.

4

• What would happen if I wanted to make six dozen
  cookies, and the recipe only called to make three
  dozen cookies? What would I have to do?

5
CaC2 2H2O ? C2H2 Ca(OH)2

• Coefficients
• 1 2 1 1
• Representations

1 Mole CaC2
2 Moles H2O
1 Mole C2H2
1 Mole Ca(OH)2
1 mole of CaC2 reacts with 2 moles of H2O to
produce 1 moles of C2H2 and 1 mole of Ca(OH)2
6
CaC2 2H2O ? C2H2 Ca(OH)2

• Mole ratio

7
CaC2 2H2O ? C2H2 Ca(OH)2

• Complete list of mole ratios

CaC2?
H2O?
C2H2?
Ca(OH)2?
8
Use the chart given in your aid packet to help
you with your mole conversions!

• This is similar to the road map you used before!

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Working a Stoichiometry Problem
A) How many moles of O2 are needed to make
7.6 g of K2O? LOOK ON THE MAP TO FIGURE OUT
HOW MANY STEPS!
1
4 K O2 ? 2 K2O
7.6 g K2O
1 mol
1 mol
K2O
O2

? mol O2
94.2 g
2 mol
K2O
K2O
0.040 mol O2
10
Try this
D) How many moles of K are needed to make
18.0 g of K2O? LOOK ON THE MAP TO FIGURE OUT
HOW MANY STEPS!
4 K O2 ? 2 K2O
1 mol
18.0 g K2O
4 mol
K2O
K

? mol K
94.2 g
K2O
2 mol
K2O
0.382 mol K
11
Working a Stoichiometry Problem
C) How many moles of O2 are needed to react with
0.56 moles of K to produce potassium oxide?
LOOK ON THE MAP TO FIGURE OUT HOW MANY STEPS!
1
4 K O2 ? 2 K2O
1 mol O2
0.56 mol K

? mol O2
4 mol K
0.14 mol O2
12
Try this
B) How many moles of K2O are produced when
1.26 moles of K to is reacted with excess
oxygen? LOOK ON THE MAP TO FIGURE OUT HOW MANY
STEPS!
4 K O2 ? 2 K2O
1.26 mol K
2 mol K2O

? mol K2O
4 mol K
0.630 mol K2O
13

• Questions???

14
Working a Stoichiometry Problem
E) How many grams of K2O will be produced from
0.50 g of K? LOOK ON THE MAP TO FIGURE OUT HOW
MANY STEPS!
4 K 1 O2 ? 2 K2O
K2O
K2O
K2O
0.50 g K
1 mol
2 mol
94.2 g
K
K2O
K2O
K2O

? g K2O
4 mol
K
K2O
K2O
1 mol
39.1 g
K
0.60 g K2O
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Try this with your partner
F) How many liters of O2 are needed to react with
2.4 grams of K? LOOK ON THE MAP TO FIGURE OUT
HOW MANY STEPS!
4 K 1 O2 ? 2 K2O
2.4 g K
1 mol K
1 mol O2
22.4L O2

? L O2
4 mol K
1 mol O2
39.1 g K
0.34 L O2
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• Questions???

17
CaC2 2H2O ? C2H2 Ca(OH)2

• Representations

1 Molecule CaC2
2 Molecules Water
1 Molecule C2H2
1 Molecule Ca(OH)2
18
CaC2 2H2O ? C2H2 Ca(OH)2

• Representations

22.4 Liter CaC2
44.8 Liters Water
22.4 Liter C2H2
22.4 Liter Ca(OH)2
19
CaC2 2H2O ? C2H2 Ca(OH)2

• How much water would I need if I started with 2
  moles of CaC2?
• Remember the coefficients 1,2,1,1
• Remember empirical formulas.
• The same ratio present in the basic equation is
  maintained all the time, no matter the multiplier
  of any coefficient.
• Answer 4

20
CaC2 2H2O ? C2H2 Ca(OH)2

• What if I wanted to make 2 moles of Ca(OH)2
  instead of just one? (Remember the cookies)
• How many moles of CaC2 would I need?
• 2
• How many moles of H2O would I need?
• 4